MIAMI-Upper- and middle-class residents of Latin America have strong per household spending power and represent a promising market for companies willing to make long-term commitments to the region.

That was the message at the Latin American Market Strategic Planning Seminar held here recently. Strategy Research Corp. sponsored the seminar, and the findings were part of its "1995 Latin American Market Planning Handbook."

Though upper-income households made up 2.6% of the total in the 37 major urban areas in 10 countries surveyed in the second half of '94, those households controlled 20.6% of all spending, or an estimated $94.8 billion in 1995.

The data could affect marketers' distribution decisions. For example, for a marketer weighing between entry into Mexico or Brazil, the total number of households in Mexico City and Sao Paulo would seem about equal (nearly 4.5 million each). But Mexico City has an estimated 1995 buying power of $119.7 billion, where Sao Paulo's is $75.4 billion.

The findings highlight trade with Latin America as the "greatest opportunity of the decade," said Richard Roffman, publisher of U.S./Latin Trade, a magazine covering trade and investment in the region. As recently as five years ago, political and economic instability hindered foreign investment. But times have changed, he said.

"Latin America was a sleeping giant. It ain't sleeping anymore," Mr. Roffman said. "Don't run from it. Embrace it. It will make you lots of money."

Strategy Research spent more than a year collecting comparative data on 37 leading Hispanic markets in Argentina, Brazil, Chile, Colombia, Ecuador, Mexico, Paraguay, Peru, Uruguay and Venezuela.

The company used such data as population size, distribution, demographics and buying power to compile its findings. It gives demographic and consumption data on eight categories-food, housing, household furnishings, clothing, healthcare, public and private transportation, leisure and education-plus other goods and services.

Marketers hoping to sell products in these emerging markets must study their markets and plan for long-term investment in the top markets, Strategy President Dick Tobin told some 200 executives at the daylong conference.

"You've got to know your markets cold," he said, adding that the findings run counter to the arguments of Ross Perot and others who question the prospects for sales of U.S.-made goods in Latin America.

"Not only does this market exist," Mr. Tobin said, "it's one of the richest markets in the world."